Art of preventing loss by evaporation from storage tanks



April 8 1924. 1,489, 725

R. E. WlLSON ART-OF PREVENTING Loss BY EVAPORATION FROM'S'IORAGE TANKS Fi led 'June' 22 1925 v jflve zdor'; Ewe/711E? Zazkwz,

1 changes and the effects of sunlight.

ROBERT E. WILSON, OF'CHICAGO, ILLINOIS, ASSIGNOR 'IO STANDARD OIL COMPANY, OF WHITING, INDIANA, A CORPORATION OF INDIANA.

ART OF PREVENTING LOSS BY EVAPORATION FROM STORAGE TANKS.

Application filed June 22, 1923. Serial No. 647,114.

To all whom it may concern:

Be it known that I, ROBERT E. VVILSQN, a citizen of the United States, residing at Chicago, in the county of Cook and State of Illmqis, have invented new and useful Improvements in the Art of Preventing Loss by Evaporation from Storage Tanks, of which the following is a specification.

This invention relates to the prevention of loss by evaporation from storage tanks containing volatile liquids, and more particularly from ,vented storage tanks containing volatile materials such as gasoline, crude petroleum and the like. It will be fully understood from the following description, illustrated by the accompanying drawings, in which apparatus for carrying the invention into effect is diagrammatically shown.

In accordance with this invention a storage tank 5 containing, for example, gasoline or other material having volatile constitutents, is connected by its sole vent 6 and a suitable conduit 7 with the inlet, preferably near the base, of acontainer 8 'in which a body of a suitable solid absorbent material 9 is provided. This absorbent material 9 may suitably rest upon a perforated plate 10, and in it are embedded a plurality of coils 11, which serve for attemperating the body ofsolid absorbent. The coils 11 are connected on the one hand to an inlet manifold 12 and on the other hand to an outlet manifold 13. An outlet from the interior of the absorbent container 8 is provided at 14:, this outlet suitably communicating with the atmosphere and being provided with a'valve 15. A man-head 16 is provided at the top of the container 8 for access to its interior.

In storage, there is normally a more or less regular expiration of vapor charged air from the tank and of fresh air back into the tank 5, resulting from the more or less regular external atmospheric tempera fiilre is breathing of the tank is more particularly noticeable in seasons and in climates when there are marked differences between day and'night temperatures. In accordance with the present invention, vapor charged air passing from the tank 5 enters and is forced through the body of absorbent material 9 in the container 8. During suction of air back into the tank, the air is sucked back through the same absorbent material in' a countercurrent direction, picking, up adsorbed Va pors. In accordancewith the present in vention, the absorbent material is so attem-perated by a suitable heating or cooling medium passing through the coils 11 as to maintain a temperature during the period of inspiration or suction higher than that prevailing during the period of expiration. This temperature differential may ordinarily be maintained by supplying through the coils ll a cooling medium durlng the warmer part of the day, during which expiration takes place- However, in some cases, instead .of cooling the body of absorbent during the period in which expiration takes place, it may be heated during the cooler hours of the night, while retraction or inspiration takes place. It is also readily apparent that both heating and cooling mediums may be applied, the cooling medium during the day and the heating medium during the night, in order to maintain this temperature differential between period of expiration and suction. The temperature control may be manual, by an operator, or may be automatic, either by a set schedule; by any suitable temperature sensitive device, whichmay be located in the vapor space of the tank or is exposed to external atmospheric changes and sunlight; or by suitable pressure sensitive device in conduit 7 operable to'cause cooling of the adsorbent during passage of vapor to it or laiealfiing during suction into the tank or Any suitable adsorbent material, such as silica gel, ferric hydroxide gel, fullers earth, activated charcoal, or the like may be employed. Such adsorbents as fullers earth.

silica gel and ferric hydroxide gel are to be preferred, as under the relatively slight temperature changes prevailing under the conditions of the present invention, these absorbents give back the absorbed vapors morereadily than adsorbents of the type of activated charcoal. The amount of the adsorbent required varies with the size of the tank and the conditions to which the latter is subjected. Thus for a 120 foottank in th mid-continent field, from 30 to 70 barrels of fullers earth'has been found satisfactory.

The temperature difi'erential to be maintained is determined largely by external 1 atmospheric conditions. During periods of inspiration or retraction into the tank, the

body of absorbent material should be maintained at a temperature at least as high as the highest temperature obtained by it during the preceding period of expiration and preferably at a temperature from 10 to 25 F, higher. For example, if the highest temperature attained by the solid absorbent material during the day, While the expiration takes place, is 90 F, the absorbent material should be maintained during the following night while suction back into the tank takes place, at a temperature of at least 90 Fuand preferably at 100 to 115 F. As already stated it is readily apparent that the temperature differentialmay be maintained by cooling the absorbent during periods of expiration, by heating it during periods of retraction both.

In carrying out the present invention, substantially all vapors of volatile-constituents of the tank are absorbed by the absorbent 9 and are to a considerable extent yielded up and returned to the tank on suction of vapor and air back into the latter. It is therefore readily apparent that under these conditions loss by evaporation is very greatly reduced.

I claim:

1. The method of preventing loss by of vapor and air, or by evaporation from a vented storage tank which comprises providing a sole outlet from the vapor space of such a tank to and through a body of solid absorbent, and attemperating the absorbent to a temperature at least as high during suction into the tank as that prevailing during expiration from the tank.

2. The method of preventing loss by evaporation from storage tanks which comprises providing a sole outlet from the vapor space from such a tank to and through a body of absorbent material,- and attemperating said absorbent material so as to'maintain its temperature during suction from 10 to 25 F higher than during expiration from the tank.

3. The method of preventing 'loss by evaporation from vented storage tanks containing volatile materials such as gasoline which comprises providing a sole outlet from the vapor. spaces from such tanks to and through a body of fullers earth, and attemperating the fullers earth so as to maintain the temperature during passage of vapor from the tank to the body of fullers earth from 10 to 25 F. higher than that prevailing on passage of vapor and air from the body of fullers earth to the tank.

ROBERT E. WILSON. 

